This invention relates to a scanning/weighing apparatus which is used, for example, with a retail terminal as part of a checkout operation in which a coded label on a purchased merchandise item is read by the scanning/weighing apparatus.
Present day checkout systems, found in supermarkets or the like, include an optical scanning unit located within the checkout counter housing for scanning bar code labels on merchandise items which are moved across a window area in the top surface of the counter. The optical scanning unit translates the bar code labels into electrical data signals which can be used to identify the merchandise item and its price. Further included in the system is a data terminal device and an electronic scale, positioned away from the optical scanning unit, for weighing produce and other types of merchandise items which are sold by weight. In determining the price of such merchandise items, prior checkout operations have required the checkout operator to remove the item to be weighed from the checkout counter and place it on the electronic scale for a weighing operation which results in a generation of data representing the weight. If a bar code label is not affixed to the merchandise item, a keyboard entry into the data terminal is also required to identify the merchandise item. The data so generated is then used by the data terminal device to calculate the purchase price of the merchandise item, to display the price and to print the price on a customer's receipt.
In order to reduce the number of movements required by the operator to check out the various types of merchandise items and to increase the speed of the checkout operation, the scale has been incorporated as part of the optical bar code reader and mounted within the checkout counter. An example of such an arrangement is disclosed in the U.S. Pat. No. 4,656,344 which is assigned to the assignee of the present application.
One of the problems found with such a scanning/weighing apparatus is that the scanning unit gets dusty or dirty and needs to be cleaned periodically. It is especially important that the scanning/weighing unit be dissembled and assembled quickly to allow the cleaning operation to be accomplished in the minimum amount of time. As fully disclosed in the previously cited United States Patent, the weighing plate is mounted on four load cells associated with the weighing beam assemblies used for weighing the merchandise items on the scale. The major portion of the overall cost of the scale is the load cells. It would be desirable to reduce the number of load cells required to produce a low cost scale without affecting the accuracy of the scale.